[BUG] Network Protocol error 1.21.11

[Iarkont]

an error occurs on the client side

`Registry loading errors:

Errors in registry minecraft:root:

Errors in element minecraft:zombie_nautilus_variant:
java.lang.IllegalStateException: Registry must be non-empty: minecraft:zombie_nautilus_variant
at amp.b(SourceFile:231)
at java.base/java.lang.Iterable.forEach(Iterable.java:75)
at amp.a(SourceFile:222)
at amp.a(SourceFile:211)
at his.a(SourceFile:93)
at his.a(SourceFile:144)
at hib.a(SourceFile:149)
at hib.a(SourceFile:113)
at hib.a(SourceFile:149)
at acj.a(SourceFile:22)
at acj.a(SourceFile:8)
at xl$a.a(SourceFile:55)
at xl.b(SourceFile:38)
at gfj.d(SourceFile:1337)
at gfj.j(SourceFile:966)
at net.minecraft.client.main.Main.main(SourceFile:250) Failed to handle packet acj@ff9d841, disconnecting
v: Registry Loading
at his.a(SourceFile:97)
at his.a(SourceFile:144)
at hib.a(SourceFile:149)
at hib.a(SourceFile:113)
at hib.a(SourceFile:149)
at acj.a(SourceFile:22)
at acj.a(SourceFile:8)
at xl$a.a(SourceFile:55)
at xl.b(SourceFile:38)
at gfj.d(SourceFile:1337)
at gfj.j(SourceFile:966)
at net.minecraft.client.main.Main.main(SourceFile:250)
Caused by: java.lang.IllegalStateException: Failed to load registries due to errors
at amp.c(SourceFile:288)
at amp.a(SourceFile:269)
at amp.a(SourceFile:236)
at amp.a(SourceFile:211)
at his.a(SourceFile:93)
... 11 more`

You can't immediately cause this error with limboapi separately, but if you install another plugin (LimboAuth) using this api, the error will manifest itself

guesses why this is happening: LimboAPI sends the registry with an empty zombie_nautilus_variant, which the 1.21.11 client rejects

version velocity: latest
LimboApi: latest build

[UserNugget]

Try to reinstall LimboAPI from https://github.com/Elytrium/LimboAPI/releases/tag/dev-build
minecraft:zombie_nautilus_variant has one entry when sent, so might be a client or mod issue.

[Iarkont]

I was just using this build for testing. And the problem is definitely not mods. The error occurs even on the vanilla client.
Of course, I'm not much of a coder, but I was able to make some changes that helped to remove the error.
limboapi\server\LimboImpl.java
line 293

 private void createRegistrySyncModern(PreparedPacket packet, ProtocolVersion from, ProtocolVersion to) {
        JoinGamePacket join = this.createJoinGamePacket(from);

        CompoundBinaryTag registryTag = join.getRegistry();
        for (String key : registryTag.keySet()) {
            CompoundBinaryTag entry = registryTag.getCompound(key);

            final String type = entry.getString("type");
            ListBinaryTag values = entry.getList("value", BinaryTagTypes.COMPOUND);

            // Skip empty registries to avoid client rejection
            if (values.size() == 0) {
                continue;
            }
.....

line 1097

          if (version.compareTo(ProtocolVersion.MINECRAFT_1_21_11) >= 0) {
            // Zombie nautilus variant
            CompoundBinaryTag zombieVariant = CompoundBinaryTag.builder()
                .putString("asset_id", "minecraft:entity/nautilus/zombie_nautilus")
                .put("spawn_conditions", ListBinaryTag.empty()).build();

            registryContainer.put("minecraft:zombie_nautilus_variant", this.createRegistry("minecraft:zombie_nautilus_variant",
                Map.of("minecraft:temperate", zombieVariant)));
          }

I hope I didn't break the rules by posting the code here.

[Iarkont]

The code that I uploaded here is the changes that helped me fix the problem. I don't deny that it's a crutch.

[UserNugget]

minecraft:zombie_nautilus_variant is required to be defined and non-empty for vanilla client to join.

I think Limbo* will still work with

// Skip empty registries to avoid client rejection
if (values.size() == 0) {
    continue;
}

removed.